[clang-format] Support generators in C++

[def-]

Bugzilla Link	38909
Version	7.0
OS	Linux
CC	@dwblaikie

Extended Description

We use lambdas to write code like:

int main()
{
    int newValue;
    If(match, [&]() {
        newValue = false;
    }).ElseIf(match2, [&]() {
        newValue = true;
    }).Else([&]() {
        newValue = false;
    });
}

Unfortunately clang-format since version 5 started indenting the ElseIf:

$ clang-format -style webkit x.cpp

int main()
{
    int newValue;
    If(match, [&]() {
        newValue = false;
    })
        .ElseIf(match2, [&]() {
            newValue = true;
        })
        .Else([&]() {
            newValue = false;
        });
}

I couldn't find an option to turn this behaviour off.

[def-]

The output has improved with clang-format 8, but the second Else is still wrongly indented:

int main()
{
    int newValue;
    If(match, [&]() {
        newValue = false;
    }).ElseIf(match2, [&]() {
          newValue = true;
      }).Else([&]() {
        newValue = false;
    });
}

[mydeveloperday]

I confirm this is still the same output in v13

int main() {
  int newValue;
  If(match, [&]() {
    newValue = false;
  }).ElseIf(match2, [&]() {
      newValue = true;
    }).Else([&]() { newValue = false; });
}

[owenca]

Adding LambdaBodyIndentation: OuterScope to the config gives the desired output.